Spraying Process for Coating a Substrate

ABSTRACT

In a spraying process for coating a substrate with a substance atomised in a stream of gas, a spray head is used to generate a stream of gas that acts upon the substrate. The substance is present in a syringe-like application container equipped with an application tip. The application tip of the application container containing the substance is introduced into the stream of gas outside the spray head at a distance therefrom and transversely with respect to the main direction of flow of the stream of gas, and the substance is introduced from the application container into the stream of gas at that location.

The present invention relates to a spraying process for coating asubstrate in accordance with the preamble of independent patent claim 1and a spray device suitable for carrying out the process in accordancewith the preamble of independent patent claim 10.

An important step during the testing of, for example, paints or paintformulations, but also, for example, adhesives and adhesiveformulations, during their development is the application of the paintor adhesive sample produced to a test substrate. A sample is applied tothe test substrate using a desired method and then, directly or after adrying phase, tested or measured in accordance with desired criteria(abrasion tests, colorimetry, chemical and physical resistance testsetc.).

As test substrate there are customarily used standard plates made ofmetal (for example plates made of steel or aluminium), cardboard, wood,glass or plastics. A widely used method for applying the sample or forcoating the test substrate with the sample is a spraying process inwhich the sample is atomised in a stream of air and the resultingdroplets of paint or adhesive are deposited or finely distributed on thesubstrate.

Comprehensive test series with different samples are often carried outin the course of the development of paints and adhesives. During suchtesting it is essential that, with each change of sample, the parts ofthe spray device used that come into contact with the sample be cleaned.The cleaning of the spray device etc. is often very laborious andrequires comparatively more time than does the actual sprayingoperation. In order to apply and test a large number of differentsamples in the shortest possible time it is important that the necessaryprocess of cleaning the application device be kept as uncomplicated andshort as possible and also that the use of large amounts of cleaningagents and solvents be reduced, because both the acquisition andespecially the disposal of the cleaning agents and solvents give rise toconsiderable cost and, in addition, are harmful to the environment.

A spray device requiring a reduced amount of cleaning is described in US2008/0012159 A1.

The spray device has a compressed-air-fed spray head (as in the case ofconventional spraying methods) which has an axial main nozzle and twohorn jet nozzles and generates a substantially conical stream of air. Anapplication container of syringe-like construction is introducibleaxially into the stream of air generated by the spray head, whichapplication container has previously picked up a substance (paintsample) to be sprayed. The application container is equipped with acannula-like tip which projects through the axial main nozzle of thespray head when the application container is installed in the spray headand has its mouth outside the spray head or rather the main nozzlethereof. By means of, for example, motor-controlled advancement of thesyringe plunger of the application container, the substance can beintroduced through the tip of the application container into the streamof air generated by the spray head, the substance then being atomised ornebulised in the stream of air. By the use of a separate applicationcontainer, the substance being sprayed does not come into contact withthe spray head, so that there is no need to clean the spray head aftereach change of substance/sample. The syringe-like application containeritself requires only a comparatively small amount of cleaning or canalso be in the form of a single-use container and discarded after eachuse.

Although the spray device known from US 2008/0012159 A1 basically solvesthe cleaning problem in such spray-coating processes, it does havevarious other disadvantages. Since the application containers areinserted into the spray head, the spray head and the applicationcontainers must be matched to one another structurally. That is to say,it is not possible to use any commercially available spray head incombination with any commercially available application container.Furthermore, the insertion and removal of the application containersrequires a relatively large amount of manipulation. And, finally,particularly the insertion of the application containers into the sprayhead and their subsequent removal therefrom constitute a notinsignificant risk of contamination which in some circumstances maystill necessitate cleaning of the spray head.

EP 2 218 513 A1 discloses a spray device for electrostatic charging andinjection of a sample solution into a stream of gas. A syringe(application container) containing the sample solution is arranged infront of the outlet of a gas pipe. The gas flowing out of the gas pipecauses the sample solution expelled from the syringe to be atomised andapplied to a substrate. Optionally, means for aligning the relativeposition between the gas pipe and the outlet from the applicationcontainer can be provided.

Whatever the method used for filling the application container withsample solution, it is also possible for that spray device to becomecontaminated with sample solution which could then, for example, fallonto the spray head or, on start-up of the stream of gas, be swept outof the application container thereby and deposited on the substrate inan uncontrolled way.

The objective of the present invention is now to provide an improvedspraying process which avoids the described disadvantages of the knownprocesses and spray devices used therefor. More specifically, theobjective is to improve a spraying process of the generic to kind to theeffect that contamination of the spray head with the substance beingsprayed is reliably avoided and that the process is easy to handle andeconomically realisable in terms of apparatus and can be carried outusing commercially available spray heads and application containers wellestablished in the sector.

The problem underlying the invention is solved by the spraying processaccording to the invention defined in independent patent claim 1 and bythe spray device defined in patent claim 10. Especially advantageousdevelopments and embodiments of the spraying process according to theinvention and the spray device according to the invention will beapparent from the respective dependent patent claims.

In respect of the spraying process, the core of the invention lies inthe following: in a spraying process for coating a substrate with asubstance atomised in a stream of gas, a spray head is used to generatea stream of gas that acts upon the substrate. The substance is presentin a syringe-like application container equipped with an application tipand, without contact with the spray head, is introduced from theapplication container into the stream of gas and thereby atomised. Theapplication tip of the application container containing the substance isintroduced into the stream of gas outside the spray head at a (small)distance therefrom and transversely with respect to the main directionof flow of the stream of gas (centrally, i.e. axially), and thesubstance is introduced from the application container into the streamof gas at that location.

Introducing the application container, or rather the application tipthereof, laterally into the stream of gas outside the spray head, on theone hand reliably avoids any kind of contamination of the spray head. Inparticular, any droplets of substance adhering to the outside of theapplication tip during the introduction of the application tip into theexisting stream of gas are blown away by the latter before they are ableto fall onto the spray head. On the other hand, any combinations ofcommercially available spray heads and application containers can beused independently of one another. Furthermore, the introduction of theapplication container, or rather the application tip thereof, into thestream of gas and its removal from the stream of gas are relativelysimple in terms of handling.

A further advantage of the spraying process according to the inventionis that the metering speed of the substance to be atomised can be variedindependently of the speed of the stream of gas.

In accordance with an advantageous embodiment, a disposable syringe or adisposable pipette can be used as application container, with the resultthat no cleaning whatsoever is required when the substance is changed.

Advantageously the application container with the application tip isselected from a set of different application containers having differentapplication tips. In particular, a variety of syringe types (for examplewith finer needles, with multi-hole needles) and especially differentsyringe volumes can be used or exchanged for one another with little orno effort.

As application container, but also as application tips, it is possibleto use a multiplicity of existing commercially available products fromthe field of pipetting in an extremely wide range of configurations (inrespect of material, size, design) which, for the sake of simplicity,are not further differentiated herein.

To achieve optimum spray results, the application tip of the applicationcontainer is advantageously arranged at a distance of 0.01-5 cm,preferably 0.1-0.5 cm, from an axial main nozzle of the spray head,measured in the main direction of flow of the stream of gas. Thatdistance is dependent, for example, upon the formulation or substancebeing applied, the type of tip, the ambient temperature, the ambienthumidity or the form of spray employed (wide jet, round jet) and it istherefore advantageous if that distance can be varied in order toachieve an optimum or desired spray result.

Advantageously a spray head is used which has two oppositely locatedhorn air nozzles which generate two inwardly directed horn gas streams,the application tip of the application container being arranged in theregion of intersection of the two horn gas streams. The additional horngas streams provide for additional nebulisation and define the shape ofthe spray result (round jet, wide jet).

During the spraying operation, that is to say while the substrate isbeing acted upon by the atomised substance, the substrate isadvantageously moved in one or two dimensions in a plane alignedtransversely with respect to the main direction of flow of the stream ofgas. Alternatively, while the substrate is being acted upon by theatomised substance, the spray head and the application container withthe application tip are moved in one or two dimensions transversely withrespect to the main direction of flow of the stream of gas. Thesubstrate is in that way coated completely and with a uniform layerthickness.

With a view to the best possible spray result, the spray head isadvantageously operated at a pressure of 1-10 bar, preferably 3-4 bar,and a gas throughput of 100-1000 l/min, preferably 200-600 l/min.

In accordance with an advantageous development, the application tips ofmore than one application container are introduced simultaneously orsequentially into the stream of gas L, and the different substances tobe sprayed that are contained in the application containers aredelivered into the stream of gas L and atomised either in succession orsimultaneously.

That form of the spraying process enables, for example, a plurality ofdifferent paint formulations F to be sprayed either immediately oneafter the other or even simultaneously, thus allowing intermixing of thedifferent paint mists FN. This would be an advantage, for example, forthe application of two-component systems, but it would in that way alsobe possible for a solvent or some other auxiliary substance to be addedto the spray mist in addition to the paint formulation F, for example inorder to compensate for the evaporation of the solvents contained in thepaint formulation at high ambient temperatures.

In respect of the spray device, the core of the invention lies in thefollowing: a spray device for carrying out the spraying processaccording to the invention comprises a spray head for generating astream of gas that acts upon the substrate and an application containerequipped with an application tip for holding a substance to be atomisedin the stream of gas. The spray device further comprises a robot,preferably a multi-axis robot, for picking up the application containerfrom a storage container and for introducing the application tip of theapplication container picked up into the spray jet generated by thespray head transversely with respect to the main direction of flow ofthe stream of gas at a position outside the spray head and at a distancetherefrom.

In the context of this invention, a robot, especially a multi-axisrobot, is to be understood as being any kind of motor-driven,electrically or electronically controlled manipulation means equippedwith gripping mechanisms which, in a controlled way, are able to griparticles and move them in at least two spatial directions.

The spray device advantageously also comprises discharge means fordischarging the substance contained in the application container fromthe application container into the stream of gas generated by the sprayhead.

Advantageously the robot is configured to remove a partly or fullyemptied application container from the stream of gas after use andpreferably throw it into a waste container.

The spray device is advantageously configured to adjust the distancebetween the spray head and the application tip and/or the distancebetween the application tip and the substrate automatically or manually.This allows adaptation to an extremely wide range of operatingconditions and optimisation of the spray pattern on the substrate.

The spray device is advantageously configured for sequential orsimultaneous introduction of the application tips of two or moreapplication containers into the stream of gas. This allows sequential orsimultaneous nebulisation of two or more substances.

Advantageously the application container is a disposable syringe or adisposable pipette which can be disposed of after use and need not becleaned.

Advantageously the application tip is straight and an outlet opening ofthe application tip opens into the stream of gas at a right-angle, sothat the substance to be applied is introducible into the stream of gasat a right-angle to the main direction of flow thereof.

In a variant that is likewise advantageous, the application tip isstraight and has at least one lateral outlet opening through which thesubstance to be applied is introducible into the stream of gas. Thesubstance to be applied is thus introducible into the stream of gas inthe main direction of flow thereof.

In an alternative advantageous variant, the application tip is bent atan angle and an outlet opening of the application tip opens in thedirection of the stream of gas, so that the substance to be applied isintroducible into the stream of gas parallel to the main direction offlow thereof.

The robot is advantageously configured to move the spray head togetherwith the application container in at least one dimension transverselywith respect to the main direction of flow of the stream of gas. It isthus possible to achieve uniform application to the substrate over theentire area thereof to be sprayed.

Alternatively or in addition, the spray device has a second robot forholding a substrate and for moving the substrate in at least onedirection transversely with respect to the main direction of flow of thestream of gas. This likewise makes it possible to achieve uniformapplication to the substrate over the entire area thereof to be sprayed.

The spray device advantageously comprises an electronic controller forthe robot and, where applicable, for the second robot, for dischargemeans for discharging substance contained in the application containerfrom the application container and for supplying gas to the spray head,the controller being programmed so that it can autonomously control theworkflows necessary for carrying out the spraying process. In this waythe spray device is able to operate automatically.

In an advantageous embodiment, the electronic controller is programmedso that it iteratively optimises the workflows and parameters necessaryfor carrying out the spraying process. The electronic controller thusprovides automated optimisation of the workflows and especially theparameters that affect the spray pattern, especially the speed of thestream of gas, metering speed of the substance discharge, distancesbetween the spray head, the application tip and the substrate, horn gasflow, etc. For that purpose, after a first spraying operation thesprayed substrate is tested in a suitable analysis device, for examplein respect of the colour and homogeneity of the paint layer, etc., thenthe spraying operation is repeated with one or more modified parameters,the new substrate is likewise tested and, by comparing the results ofthe first and subsequent tests, a decision is made as to whether themodification of the parameters has led to an improvement or adeterioration in the spray result. It is thus possible for the optimumparameters for the spraying to operation to be automatically determinediteratively over a plurality of spraying operations and subsequenttesting of the spray results. In detail, such an iterative optimisationprocess could look like this:

-   -   1) Spraying of a substance, for example paint, onto a substrate        using a parameter set A.    -   2) Analysis of the substrate for inhomogeneities in an analysis        device, the analysis device detecting, for example,        inhomogeneities, e.g. in the form of small bubbles on the paint        surface.    -   3) The spraying process is repeated, but using a parameter set B        that has been slightly modified in comparison with parameter set        A by the software of the control computer, for example in which        the intensity of the stream of gas has been slightly reduced.    -   4) The analysis is repeated and, for example, already shows a        lower level of bubble formation.    -   5) A further spraying operation is carried out, using a        parameter set C that has likewise been adapted by the software        of the control computer (for example in this case with a slight        reduction in the speed of discharge of the paint into the stream        of gas).    -   6) A further analysis of the new spray result now shows, for        example, that the sprayed-on paint layer no longer exhibits any        inhomogeneities.    -   7) The software of the electronic controller stores the        optimised parameter set C and uses it for further spraying        operations.

The invention is described in greater detail below with reference toexemplary embodiments shown in the drawings, wherein:

FIG. 1a -1 d—are a diagrammatic representation of an exemplaryembodiment of the spraying process according to the invention,

FIG. 2a -2 d—are a side view, a plan view, a front view and a sectionalview of a spray head suitable for the spraying process according to theinvention,

FIG. 3—is a diagrammatic side view of an exemplary embodiment of thespray device according to the invention in the non-operating state,

FIG. 4—is a plan view of the spray device of FIG. 3 in a state in whichit is ready for the spraying operation,

FIG. 5—is a side view analogous to FIG. 3 of the spray device during aspraying operation,

FIG. 6—is a diagram illustrating the movement of a substrate relative tothe spray head,

FIG. 7a -b—are diagrams showing two possible forms of application tipsand

FIG. 8—shows the spray device in an exemplary embodiment that has beenslightly modified in comparison with the exemplary embodiment accordingto FIG. 5.

The following observations apply in respect of the description whichfollows: where, for the purpose of clarity of the drawings, referencesigns are included in a Figure but are not mentioned in the directlyassociated part of the description, reference should be made to theexplanation of those reference signs in the preceding or subsequentparts of the description. Conversely, to avoid overcomplication of thedrawings, reference signs that are less relevant for immediateunderstanding are not included in all Figures. In that case, referenceshould be made to the other Figures.

Hereinbelow the invention is described purely by way of example inconnection with the spray application of a liquid paint formulation to asubstrate. It will be understood, however, that the process according tothe invention and the corresponding device according to the inventionare in principle also suitable for the spray application of substancesother than paint formulations or adhesives and adhesive formulations,provided the substances in question are suitable for atomisation ornebulisation (aerosol formation) in a stream of air or, more generally,gas. As well as liquid substances, in principle substances in powderform also come into consideration for spray application.

Compressed air is normally used for atomisation or nebulisation of thesubstance, but it is also possible to use any other gas or gaseousmixture for that purpose. For the sake of simplicity the followingexplanation is confined to a paint formulation as the substance beingapplied and (compressed) air as the gaseous mixture used for thenebulisation or atomisation of the substance.

FIGS. 1a-1d show the typical steps of the spraying process according tothe invention.

A substance to be applied here in the example a liquid paint formulationF is held in readiness in a storage container V (FIG. 1a ). A desired(relatively small) amount of the paint formulation F is drawn up fromthe storage container V into an application container 10 (FIG. 1b ). Theapplication container 10 is syringe-like and has a chamber 11, a plunger12 axially displaceable therein, a plunger rod 13 and an application tip14. In practice, a commercially available disposable syringe or a(plunger) pipette is advantageously used as application container 10.The application tip 14 is advantageously configured as a commerciallyavailable metering needle or cannula.

Those two preparative steps just described can also take place outsidethe actual spraying process, with a desired number of applicationcontainers 10 being provided that have different contents or the samecontents, as the case may be.

For the spraying process, a spray head 20 is used to generate asubstantially conical stream of air (or generally a stream of gas) L,the spray head 20 being arranged in front of and at a distance from a(flat) substrate S to be sprayed so that the stream of air L acts uponthe substrate S (FIG. 1c ). During operation, the spray head 20 isconnected to a compressed air source (not shown) via a supply line 21.The pressure of the compressed air is, for example, 3-4 bar; the airthroughflow rate is, for example, 200-600 l/min.

The application tip 14 of the application container 10 is introducedlaterally into the stream of air L generated by the spray head 20, thatis to say transversely with respect to the main direction of flow of thestream of air L, so that the free end (the outlet opening) of theapplication tip 14 is located approximately centrally (axially) in thestream of air L at a relatively small axial distance ds (FIG. 2d ) fromthe spray head 20.

By axial displacement of the plunger 12 in the chamber 11 of theapplication container 10, paint formulation F is introduced from theapplication container 10 into the stream of air L, where it is atomised.The spray mist consisting of the mixture of air and extremely smallpaint droplets is indicated by FN in FIG. 1 d. The spray mist FN actsupon the substrate S and produces a patch of coating FS thereon.

The outlet opening of the application tip 14 of the applicationcontainer 10 must be sufficiently small to deliver very fine droplets ofthe paint formulation F into the stream of air L. The distance ds of theapplication tip 14 from the spray head 20, or rather the main nozzle 24thereof, is only a few millimetres, typically about 0.01-5 cm. Theapplication tip 14 can be straight, as shown as 14 a in FIG. 7 a, andproject into the stream of air L at a right-angle, so that the outletopening of the tip is likewise located at a right-angle to the stream ofair, or, as shown in FIG. 7 b, is in the form of a curved applicationtip 14 b in which the front portion of the tip is bent over so that theoutlet opening of the tip lies parallel to the stream of air.Alternatively, the application tip can also be provided with one or morelateral outlet openings. It is also possible for the outlet opening ofthe application tip to open into the stream of air at angles other thana right-angle or parallel to the main direction of flow of the stream ofair L.

In order to apply a homogeneous paint layer to the entire area of thesubstrate S to be sprayed, the substrate S, for example as shown in thediagram in FIG. 6, is moved in one or two directions (horizontallyand/or vertically) in its own plane. This can also be advantageous if acoating is to be applied to an area of the substrate S that is largerthan can immediately be acted upon by the spray mist FN. A possibletravel path of the substrate S is indicated by 65 in FIG. 6. The axialdistance between the substrate S and the spray head 20 remains constant,but in an advantageous implementation could also be adjusted during aspraying operation or between a plurality of spraying operations. As analternative to the movement of the substrate S, it is also possible forthe spray head 20 together with the application tip 14 of theapplication container 10 to be moved in one or two dimensionstransversely with respect to the direction of flow of the spray mist FN.

A commercially available spray head can be used as spray head 20. Anexample of a suitable spray head 20 is shown in FIGS. 2a-2d in a drawingshowing three views (FIGS. 2a-c ) and a sectional view (FIG. 2d ).

The spray head 20 has a housing 22, at one end of which there isarranged an inlet 23 for the connection of the compressed air supplyline 21 (FIG. 1c ). At the other end of the housing there are arrangedan axial main nozzle 24 and two diametrically opposite horn air nozzles(or, generally, horn gas nozzles) 25. The axial main nozzle 24 and thetwo horn air nozzles 25 are in communicating connection with the inlet23 via ducts 26 and 27, respectively, provided in the housing 22. Themain nozzle 24 and the two horn air nozzles 25 together generate theafore-mentioned, substantially conical air jet L which, as a result ofthe inwardly directed, advantageously adjustable horn air streams (or,generally, horn gas streams) generated by the two horn air nozzles 25,can be varied in shape between a wide jet and a round jet.

It would also be possible to use as spray head 20 a commerciallyavailable spray head having (a) feed opening(s) for the substance to besprayed, in which case, however, its feed opening(s) for substance to besprayed would be inactive or closed, that is to say the spray head wouldserve only for generating the stream of gas.

FIGS. 3-5 show an exemplary embodiment of a complete spray device whichis suitable for carrying out the spraying process according to theinvention fully automatically.

The spray device is constructed on a base plate 1. On the base plate 1there are arranged a first multi-axis robot 30, a holder 40 for thespray head 20, a holder 50 for an application container 10, a secondmulti-axis robot 60 and a spray chamber 70. Also located on the baseplate 1 are a magazine 81 for a supply of application containers 10, awaste container 82 for empty or discarded application containers 10 anda collecting container 90 for receiving finished sprayed substrates S.

The first (multi-axis) robot 30 constructed on a mounting frame 31comprises as main element a multi-axis robot arm 32, on the foremost endof which there is arranged a gripping mechanism 33 for taking hold of anapplication container 10. The holder 40 is essentially a pedestal. Thespray head 20 is mounted at its upper end. The spray head is (duringoperation of the device) connected to a compressed air source (notshown) via the supply line 21. The holder 50 is likewise essentially apedestal, at the upper end of which there are arranged a receivingdevice 51 and a guide 52 (FIG. 4) for an application container 10. Onthe holder 50 there is also arranged a drive device 53 for the plunger12 of an inserted application container 10 (FIG. 4). This drive devicecan be an advancing drive, as known, for example, from fully automaticpipetting systems. The plunger 12, the plunger rod 13 and the drivedevice 53 together form discharge means for discharging the substancelocated in the application container 10 into the stream of gas L.

The second multi-axis robot 60, which is likewise constructed on amounting frame 61, comprises as main element a robot arm 62 which,similarly to an XY table, can be moved vertically (perpendicular to thebase plate 1) and horizontally (perpendicular to the plane of thedrawing). At the free end of the robot arm 62 there is arranged aholding device 63 for a substrate S to be coated. The holding device 63can be, for example, in the form of a vacuum holding device which(during operation) is connected to a vacuum source or source of reducedpressure (not shown) via a line 64.

The spray chamber 70 forms an extractor for stray spray mist, i.e. spraymist bypassing the substrate, which is advantageously provided with afilter and is connected to a suction device (not shown) via a suctiontube 71.

The relative arrangement of the described components of the spray devicecan be seen clearly from FIG. 3 (side view) and FIG. 4 (view fromabove).

The spray device further comprises an electronic controller 100 whichactuates the two multi-axis robots 30 and 60, the drive device 53 foradvancing the plunger 12 of the application container, as well as thenecessary valves (vacuum, spray head control). The controller 100 neednot necessarily be arranged on the base plate 1, but can also berealised, for example, by an appropriately connected external computer.The controller 100 can also be configured so that, by means of adjustingmeans (not shown herein), it adjusts the distance between theapplication tip of the application container and the spray head andoptionally also the distance between the application tip of theapplication container and the substrate, either as a result of a manualcommand or automatically on the basis of, for example, an analysis ofthe spray pattern on the substrate.

FIG. 3 shows the spray device in the non-operating configuration. Themagazine 81 holds a number of pre-filled application containers 10. Asubstrate S to be sprayed is held in place on the holding device 63 ofthe second multi-axis robot 60.

The mode of operation of the spray device is as follows, all theworkflows being initiated and controlled by the controller 100:

In response to the start command of the controller 100, the arm 32 ofthe first multi-axis robot 30 is moved over the magazine 81 and with itsgripping mechanism 33 picks up an application container 10 held inreadiness therein. The application container 10 is then moved by themulti-axis robot 30 to the storage container V and the tip of theapplication container is dipped into the paint formulation F. Here adesired (relatively small) amount of the paint formulation F is suckedinto the application container 10 by withdrawal of the plunger 13 (seeFIG. 1b ). The arm 32 of the multi-axis robot 30 then moves over theholder 50 and travels with the application container 10 into thereceiving device 51 and guide 52 of the holder (FIG. 4). As described inconnection with FIGS. 1c and 1 d, the tip 14 of the applicationcontainer 10 is located in front of the spray head 20 and at an axialdistance therefrom essentially approximately in the centre of the streamof air L generated by the spray head 20. Advantageously the distancebetween the spray head 20 and the application tip 14 can be alteredautomatically during the spraying operation or manually betweenindividual spraying operations in such a way that the spray pattern(affects patch of coating FS) can be adjusted in respect of size andpaint mist density.

Once the spray head 20 has been activated and the said stream of air isstable, the drive device 53 on the holder 50 displaces the plunger 12 ofthe application container 10, the paint formulation F located in theapplication container 10 gradually being introduced from the latter intothe stream of air L and, by its atomisation, forming a paint formulationmist FN which in turn acts upon the substrate S (FIG. 5). The movementof the plunger 12 of the application container 10 can alternatively alsobe effected by the first multi-axis robot 30 by means of its grippingmechanism 33. The speed with which the paint formulation F is deliveredinto the stream of air L, and/or the stream of air itself (amount ofair, air speed), can be varied in order to alter the spray pattern.

If necessary, during the spraying operation the substrate S can be movedup and down as well as back and forth by means of the second multi-axisrobot 60, as shown in the diagram in FIG. 6. Advantageously, thedistance between the application tip 14 and the substrate S can bealtered during the spraying operation or manually between individualspraying operations in such a way that the spray pattern (affects patchof coating FS) can be adjusted in respect of size and spray mistdensity.

After the end of the spraying operation, the application container 10 isthrown into the waste container 82 by means of the first multi-axisrobot 30. The finished sprayed substrate S is then deposited in thecollecting container 90. This too can be effected, for example, by meansof the first multi-axis robot 30 insofar as it is equipped with suitablemechanisms for taking hold of the substrate.

If necessary, the described workflows are repeated with a freshsubstrate and a fresh application container.

As shown in FIG. 8, a further advantageous embodiment of the spraydevice according to the invention has, instead of the first and secondrobots, a single multi-function robot 130 which assumes the functions ofthose two robots: the multi-function robot 130 picks up, for example,the application container 10 with the application tip 14 and fixes themin a spraying tool 120, which is stored on a parking station 110, can bepicked up by the multi-function robot and has an inbuilt spray head 20and an application container holder 51 including the drive 53 (thelatter two components not being shown in FIG. 8 for clarity of thedrawing), then picks up that spraying tool 120 and, during the sprayingoperation, moves it along a substrate S which is fixedly mounted on asubstrate holder 66 (see also FIG. 6).

In a further embodiment, not shown in the drawings, the spray device isconfigured to introduce the application tips 14 of more than oneapplication container 10 simultaneously or sequentially into the streamof air L of the spray head 20. This enables a plurality of differentpaint formulations F to be sprayed either immediately one after theother or even simultaneously, thus allowing intermixing of the differentpaint mists FN. This is an advantage, for example, for the applicationof two-component systems, but it would in that way also be possible fora solvent or some other auxiliary substance to be added to the spraymist in addition to the paint formulation F, for example in order tocompensate for the evaporation of the solvents contained in the paintformulation at high ambient temperatures.

1. A spraying process for coaling a substrate with a substance atomisedin a stream of gas, wherein a spray head is used to generate a stream ofgas that acts upon the substrate, and wherein the substance is presentin a syringe-like application container equipped with an application tipand, without contact with the spray head, is introduced from theapplication container into the stream of gas and thereby atomised,wherein the application tip of the application container containing thesubstance is introduced into the stream of gas outside the spray head ata distance therefrom and transversely with respect to the main directionof flow of the stream of gas, and the substance is introduced into thestream of gas at that location.
 2. The spraying process according toclaim 1, wherein a disposable syringe or a disposable pipette is used asthe application container.
 3. The spraying process according to claim 1,wherein the application container with the application tip is selectedfrom a set of different application containers having differentapplication tips.
 4. The spraying process according to claim 1, whereinthe application tip of the application container is arranged at adistance of 0.01-5 cm from an axial main nozzle of the spray head,measured in the main direction of flow of the stream of gas.
 5. Thespraying process according to claim 1, wherein a spray head is usedwhich has two oppositely located horn air nozzles which generate twoinwardly directed horn gas streams, and the application tip of theapplication container is arranged in a region of intersection of the twohorn gas streams.
 6. The spraying process according to claim 1, whereinthe substrate, while being acted upon by the atomised substance, ismoved in one or two dimensions transversely with respect to the maindirection of flow of the stream of gas.
 7. The spraying processaccording to claim 1, wherein, while the substrate is being acted uponby the atomised substance, the spray head and the application containerwith the application tip are moved in one or two dimensions transverselywith respect to the main direction of flow of the stream of gas.
 8. Thespraying process according to claim 1, wherein the spray head isoperated at a pressure of 1-10 bar and a gas throughput of 100-1000l/min.
 9. The spraying process according to claim 1, wherein theapplication tips of more than one application container are introducedsimultaneously or sequentially into the stream of gas, and the differentsubstances to be sprayed that arc contained in the applicationcontainers are delivered into the stream of gas 4 and atomised either insuccession or simultaneously.
 10. A spray device for carrying out thespraying process according to claim 1, having a spray head forgenerating a stream of gas that acts upon the substrate and anapplication container equipped with an application tip for holding asubstance to be atomised in the container from a storage container andfor introducing the application tip of the application container pickedup into the stream of gas generated by the spray head transversely withrespect to the main direction of flow of the stream of gas at a positionoutside the spray head and at a distance therefrom.
 11. The spray deviceaccording to claim 10, further comprising a discharger configured todischarge the substance contained in the application container from theapplication container into the stream of gas generated by the sprayhead.
 12. The spray device according to claim 10, wherein the robot isconfigured to remove a partly or fully emptied application containerfrom the stream of gas.
 13. The spray device according to claim 10,wherein the spray device is configured to adjust the distance betweenthe spray head and the application tip and/or the distance between theapplication tip and the substrate automatically or manually.
 14. Thespray device according to claim 10, wherein the spray device isconfigured for sequential or simultaneous introduction of theapplication tips of two or more application containers into the streamof gas.
 15. The spray device according to claim 10, wherein theapplication container is a disposable syringe or a disposable pipette.16. The spray device according to claim 10, wherein the application tipis straight and an outlet opening of the application tip opens into thestream of gas at a right-angle, so that the substance to be applied isintroducible into the stream of gas at a right-angle to the maindirection of flow thereof.
 17. The spray device according to claim 10,wherein the application tip is straight and has at least one lateraloutlet opening through which the substance to be applied is introducibleinto the stream of gas.
 18. The spray device according to claim 10,wherein the application tip is bent at an angle and an outlet opening ofthe application tip opens in the direction of the stream of gas, so thatthe substance to be applied is introducible into the stream of gasparallel to the main direction of How thereof.
 19. The spray deviceaccording to claim 10, wherein the robot is configured to move the sprayhead together with the application container in at least one dimensiontransversely with respect to the main direction of flow of the stream ofgas.
 20. The spray device according to claim 10, further comprising asecond robot for holding a substrate and for moving the substrate in atleast one direction transversely with respect to the main direction offlow of the stream of gas.
 21. The spray device according to claim 10,further comprising an electronic controller for the robot, for a secondrobot for holding a substrate, for a discharger for discharging thesubstance contained in the application container from the applicationcontainer, and/or for supplying gas to the spray head, the controllerbeing programmed to autonomously control the workflows necessary forcarrying out the spraying process.
 22. The spray device according toclaim 21,. wherein the electronic controller is programmed so that ititeratively optimises the workflows and parameters necessary forcarrying out the spraying process.